Samples of (100) n-type material were implanted with 3.6MeV 12C ions, at temperatures ranging from -110 to 400C, to doses of between 107 and 2 x 109/cm2. Deep-level transient spectroscopy was then used to study the samples. It was found that the deep-level transient spectra were dominated by peaks which were normally associated with vacancy-O and di-vacancy centers. The heights of the peaks changed with temperature. In particular, the level which originated from the doubly negative charge state of V2 increased by about 50% between -110 and 300C. This was not attributed to an increase in the V2 concentration, but was instead assumed to reflect a relaxation of the strain in the lattice which surrounded the V2 centers. At temperatures above about 300C, V2 ceased to be stable and new energy levels appeared. At doses below 107/cm2, at 400C, a major new peak emerged at Ec-0.57eV. Its nature was unknown, but it was thought to involve impurities in the as-grown material.

J.Lalita, C.Jagadish, B.G.Svensson: Nuclear Instruments and Methods in Physics Research B, 1995, 106[1-4], 237-41